Schwann cells

In the same way that
oligodendrocytes support
axons and produce myelin in the
central nervous system, so also do Schwann cells support axons in the
peripheral nervous system. Most axons in the peripheral nervous system are
myelinated, as compared with with the central nervous system.

One oligodendrocytes can create multiple myelin segments with its many
'tentacles'. One Schwann cell, by contrast, creates only one myelin segment by
coiling itself fully around a part of the axon.

If the axon is damaged, the Schwann cells will not only help absorb the dead
axon but will also align to form a tube for a new axon to be grown in. When an
axon dies, the neuron grows multiple 'sprouts'. When one of these finds the
Schwann tube, it grows quickly through it (at 3-4 mm/day) whilst the other
sprouts wither.

Central nervous system cells do not regenerate in this way. Schwann
myelin is also resistant to the attack of multiple sclerosis -- unlike the
oliodendrocytemyelin in the central nervous system.